单选题Less Is More It sounds all wrong-drilling holes in a piece of wood to make it more resistant to knocks. But it works because the energy from the blow gets distributed throughout the wood rather than focusing on one weak spot. The discovery should lead to more effective and lighter packaging materials. Carpenters have known (1) centuries that some woods are tougher than others. Hickory (山核桃木), for example, was turned into axe handles and cartwheel spokes (轮辐) because it can absorb shocks without breaking. White oak, for example, is much more easily damaged, (2) it is almost as dense. Julian Vincent at Bathe University and his team were convinced the wood's internal structure could explain the differences. Many trees have tubular (管的) vessels that run (3) the trunk and carry water to the leaves. In oak they are large, and arranged in narrow bands, but in hickory they are smaller, and more evenly distributed. The researchers (4) this layout might distribute a blow's energy throughout the wood, soaking up a bigger hit. To test the idea, they drilled holes 0.65 millimetres across into a block of spruce (云杉), a wood with (5) vessels, and found that (6) with stood a harder knock. (7) when there were more than about 30 holes per square centimetre did the wood's performance drop off. A uniform substance doesn't cope well with knocks because only a small proportion of the material is actually (8) . All the energy from the blow goes towards breaking the material in one or two places, but often the pieces left (9) are pristine (未经破坏的). But instead of the energy being concentrated in one place, the holes provide many weak spots that all absorb energy as they break, says Vincent. "You are controlling the places (10) the wood breaks, and it can then absorb more (11) , more safely. " The researchers believe the principle could be applied to any material- (12) example, to manufacture lighter and more protective packaging. It could (13) be used in car bumpers, crash barriers and arm our for military vehicles, says Ulrike Wegst, (14) the Max Plank Institute for Mental Research in Stuttgart. But she emphasizes that you (15) to design the substance with the direction of force in mind. "The direction of loading is crucial," she says.

单选题The policemen acted quickly because lives were at stake .

单选题Flying the Hypert Skies A little airplane has given new meaning to the term "going hyper." The Hyper-X recently broke the record for air-breathing jet planes when it traveled at a hypersonic speed of seven times the speed of sound. That's about 5,000 miles per hour. At this speed, you'd get around the world -- flying along the equator -- in less than 5 hours. The Hyper-X is an unmanned, experimental aircraft just 12 feet long. It achieves hypersonic speed using a special sort of engine known as a scramjet. It may sound like something from a comic book, but engineers have been experimenting with scramjets since the 1960s. For an engine to burn fuel and produce energy, it needs oxygen. A jet engine, like those on passenger airplanes, gets oxygen from the air. A rocket engine typically goes faster but has to carry its own supply of oxygen. A scramjet engine goes as fast as a rocket, but it doesn't have to carry its own oxygen supply. A scramjet's special design allows it to obtain oxygen from the air that flows through the engine. And it does so without letting the fast-moving air put out the combustion flames. However, a scramjet engine works properly only at speeds greater than five times the speed of sound. A booster rocket carried the Hyper-X to an altitude of about 100,000 feet for its test flight. The aircraft's record-beating flight lasted just 11 seconds. Although the little plane's self-powered flight lasted only 11 seconds, that brief journey on March 27 makes a major milestone on the way to a new breed of very fast airplanes, comments Werner J. A. Dahm of the University of Michigan in Ann Arbor. In the future, engineers predict, airplanes equipped with scramjet engines could transport cargo quickly and cheaply to the brink of space. Such hypersonic jets could potentially carry passengers anywhere in the world in just a few hours. Out of the three experimental Hyper-X aircrafts built for NASA, only one is now left. The agency has plans for another 11-second hypersonic flight, this time at 10 times the speed of the sound.

单选题The frame needs to be strong enough to support the engine.

单选题The dentist has decided to extract her bad tooth. A. pull out B. repair C. take D. dig

单选题The two boys in Chicago were A. shot. B. murdered. C. accused. D. sentenced.

单选题How do you Uaccount for/U your absence from the class last Thursday?

单选题In general, the British people belong to one of the more affluent countries of Europe and enjoy a high standard of living compared to the rest of the world.

单选题The Cherokee Nation Long before the white man came to America, the land belonged to the American Indian nations. The nation of the Cherokees lived in what is now the southeastern part of the United States. After the white man came, the Cherokees copied many of their ways. One Cherokee named Sequoyah saw how important reading and writing was to the white man. He decided to invent a way to write clown the spoken Cherokee language. He began by making word pictures. For each word he drew a picture. But that proved impossible--there were just too many words. Then he took the 85 sounds that made up the language. Using his own imagination and an English spelling book, Sequoyah invented a sign for each sound. His alphabet proved amazingly easy to learn. Before long, many Cherokees knew how to read and write in their own language. By 1828, they were even printing their own newspaper. In 1830, the U.S. Congress passed a law. It allowed the government to remove Indians from their lands. The Cherokees refused to go. They had lived on their lands for centuries. It belonged to them. Why should they go to a strange land far beyond the Mississippi River? The army was sent to drive the Cherokees out. Soldiers surrounded their villages and marched them at gunpoint into the western territory. The sick, the old and the small children went in carts, along with their belongings. The rest of the people marched on foot or rode on horseback. It was November, yet many of them still wore their summer clothes. Cold and hungry, the Cherokees were quickly exhausted by the hardships of the journey. Many dropped dead and were buried by the roadside. When the last group arrived in their new home in March 1839, more than 4,000 had died. It was indeed a march of death.

单选题His sincerity added much more credibility to the words.

单选题"I'm not meddling". Mary said Umildly/U. "I'm just curious".

单选题{{B}}第三篇{{/B}} Teaching Poetry No poem should ever be discussed or "analyzed" , until it has been read aloud by someone, teacher or student. Better still, perhaps, is the practice of reading it twice, once at the beginning of the discussion and once at the end, so the sound of the poem is the last thing one hears of it. All discussion of poetry are, in fact, preparations for it aloud, and the reading of the poem is, finally, the most telling "interpretation" of it, suggesting tone, rhythm, and meaning all at once. Hearing a poet read the work in his or her own voice, on records or on film, is obviously a special reward. But even those aids to teaching can not replace the student and teacher reading of it or,best of all, reciting it. I have come to think, in fact, that time spent reading a poem aloud is much more important than "analyzing" it, if there isn't time for both. I think one of our goals as teachers of English is to have students love poetry. Poetry is "a criticism of life", "a heightening of life, enjoyment with others". It is "an approach to the truth of feeling", and it "can save your life". It also deserves a place in the teaching of language and literature more central than it presently occupies. I am not saying that every English teacher must teach poetry. Those who don't like it should not be forced to put that dislike on anyone else. But those who do teach poetry must keep in mind a few things about its essential nature, about its sounds as well as its sense, and they must make room in the classroom for hearing poetry as welt as thinking about it.

单选题You look {{U}}smart{{/U}} in the new suit. A. clever B. handsome C. loyal D. brave

单选题In general, the Western experts' attitude towards TCM is_____.

单选题Marsha confessed that she knew nothing of computer.A. admittedB. reportedC. hopedD. answered

单选题A person who suffers from stage fright is easily {{U}}intimidated{{/U}} by a large audience.

单选题It's impolite to {{U}}cut in{{/U}} when two persons are holding a conversation.

单选题How Animals Keep Warm Man has invented ways to keep warm, but how do animals defend themselves? They cannot reason in the sense that man can, but nature has taken care of the animal kingdom by providing animals with special instincts. One of these instincts is known as hibernation. "Sleeping like a dormouse" is not only a common saying but is a reality. When winter comes, the dormouse and other hibernating animals have reached a well-nourished state. They eat very well in warmer days laying down fat in the tissues of their bodies and during hibernation this keeps them alive. Safe in their nests, or burrows, they sleep soundly until the warmth of spring arrives. Bats, tortoises, snakes, frogs, even insects like butterflies, hibernate more or less completely. Some, like the squirrels, sleep during coldest weather but are roused by a warm spell. During hibernation, the temperature of an animal's body drops drastically. Breathing and heart-beats almost cease. Another instinctive method of avoiding intense cold is to escape by means of migration. Wild swans, seagulls, swallows and cuckoos are a few of the very many kinds of birds which fly thousands of miles, twice a year, to avoid cold. Many animals, especially those of the Arctic reindeer of Europe, move southward towards the forests when winter approaches. They return to the northern area when the warmth of spring begins to be sensed. There are animals which do not attempt to leave at the first sign of winter cold. Their instinctive means of defense is to dig out a deep burrow, made soft and warm by padding out with straw, leaves, moss and fur. In it they have a "secret place" containing food which they hope will last the winter through! Animals which fall into this class include the Arctic fox, the rabbit and the ermine, and the little field-mice.

单选题For urban areas this approach was {{U}}wholly {{/U}} inadequate

单选题Exclusive information is more persuasive than widely known data.